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1 Revision # 2 – January 31st, 2014 2 3 Determination of the concentration of asbestos minerals in highly 4 contaminated mine tailings. The example of the abandoned mine waste 5 of Crètaz and Èmarese (Valle d’Aosta, Italy). 6 1, 1 1 7 ALESSANDRO F. GUALTIERI, * SIMONE POLLASTRI, NICOLA BURSI GANDOLFI, 1 2 3 8 FRANCESCO RONCHETTI, CARLO ALBONICO, ALESSANDRO CAVALLO, GIOVANNA 4 4 5 9 ZANETTI, PAOLA MARINI, AND ORIETTA SALA 10 1Dipartimento di Scienze Chimiche e Geologiche, Università di Modena e Reggio Emilia, I-41121 Modena, 11 Italy 12 2A.R.P.A. Valle d’Aosta, I-11020 Saint Christophe Aosta,Italy 13 3Dipartimento di Scienze dell'ambiente e del territorio e di Scienze della terra, Università di Milano- 14 Bicocca, I-20126 Milano, Italy 15 4Dipartimento di Ingegneria delle Materie Prime DIATI - Politecnico di Torino, I-10129 Torino, Italy 16 5A.R.P.A. Emilia Romagna, Sezione Provinciale di Reggio Emilia 17 I-42122, Reggio Emilia, Italy 18 19 Submitted to The American Mineralogist 20 *Corresponding author. 21 Phone: +39 059 2055810; Fax: +39 059 2055887 22 E-mail address: [email protected] 23 ______________________________________________________________________ 1 24 ABSTRACT 25 For the first time, this work reports concentration maps of asbestos minerals in 26 contaminated mine tailings drawn using the results of Rietveld quantitative phase 27 analysis (QPA). The investigates sites are located in the Valle d’Aosta region (Italy): 28 Crètaz, the most important Italian magnetite mine, active until 1979 and Emarèse, one the 29 most important chrysotile asbestos mines in Italy, active until 1968. The results of the 30 study permit to draw the spatial distribution of the asbestos (chrysotile and tremolite in 31 this specific case) concentration, useful to plan reclamation of the sites, with priority 32 given to the areas with the highest asbestos concentration. Because of the complexity of 33 the mineral assemblage which includes, among the others, antigorite, chlorite, talc, and 34 tremolite, the concentration of chrysotile was cross-checked using different experimental 35 techniques such as X-Ray powder diffraction (XRPD), Fourier Transform Infra-Red 36 (FTIR) spectroscopy, scanning electron microscopy (SEM), Polarized light Optical 37 Microscopy (PCOM), and differential thermal analysis (DTA). The accuracy of the 38 results was validated by analyzing standard samples with known concentrations of 39 chrysotile and tremolite. The comparison allowed to point out the advantages and 40 disadvantages of each experimental method. 41 At Crètaz, chrysotile ranges from 4.4 to 22.8 wt% and tremolite from 1.0 to 10.3 wt% 42 whereas at Emarèse the concentration of chrysotile varies from 3.3 to 39.5 wt% and 43 tremolite from 5.9 to 12.4 wt%. Antigorite and chlorite are the major accompanying 44 phases with variable amounts of other accessory minerals including magnetite, 45 carbonates, talc, olivine, pyroxene, talc, and brucite. The results of our study are of key 46 importance for the local environmental policies as the knowledge of the spatial 2 47 distribution of the asbestos concentration allows to plan a detailed reclamation agenda of 48 the contaminated sites. The spots with the highest surface contamination of both 49 chrysotile and tremolite were identified and classified as priority area in the reclamation 50 plan. 51 Keywords: Chrysotile, tremolite, serpentine, mine tailings, quantitative determination 52 53 INTRODUCTION 54 Commercial asbestos minerals are classified into two groups: serpentine and 55 amphibole asbestos, both sharing the same fibrous-asbestiform crystal habit but different 56 structural arrangements at the molecular scale (Bailey 1988). The fibrous-asbestiform 57 variety of serpentine is chrysotile (white asbestos) with ideal chemical formula 58 Mg3(OH)4Si2O5. The amphibole asbestos family includes five minerals: actinolite, 59 amosite (fibrous variety of grunerite, brown asbestos), anthophyllite, crocidolite (fibrous 60 variety of riebeckite, blue asbestos), and tremolite. Amphiboles’ have general formula 2+ 2+ 2+ 61 AB2C5T8O22W2 with A = , Ca, K, Li, Na; B = Ca, Fe , Li, Mg, Mn , Na; C = Fe , 62 Fe3+, Li, Mg, Mn2+, Mn3+, Ti4+; T = Al, Si, Ti4+; W = Cl, F, O2-, (OH). The ideal 63 (approximated) formulas of the five asbestos species are: actinolite A = , B = Ca, C = 64 (Fe2+, Mg), T = Si; W = (OH); amosite A = , B = C = Fe2+, T = Si; W = (OH); 65 anthophyllite A = , B = C = Mg, T = Si; W = (OH); crocidolite A = , B = Na, C = 66 (Fe2+, Fe3+, Mg), T = Si; W = (OH); tremolite A = , B = Ca, C = Mg, T = Si; W = (OH). 67 The six asbestos minerals exhibit outstanding chemical-physical and technological 68 properties exploited for various industrial applications. Chrysotile has been the most 69 commonly used form of asbestos. Regrettably, the unique fibrous-asbestiform crystal 3 70 habit and surface activity, responsible for the excellent technological properties, also 71 seem to be the cause of asbestos minerals’ potential health hazard. The history of the 72 epidemiological reports of asbestos related diseases is well described in Skinner et al. 73 (1988). Although many epidemiological studies provided evidence that amphibole 74 asbestos minerals are more hazardous than chrysotile (Hodgson and Darnton 2000), all 75 six asbestos mineral species are assumed to be harmful to human health. Exposure 76 through inhalation of asbestos minerals may provoke lung diseases (Skinner et al. 1988; 77 Dilek and Newcomb 2003) and during the 1980s, asbestos minerals were declared proven 78 human carcinogens by the US Environmental Protection Agency, the International 79 Agency for Research on cancer (IARC) of the World Health Organization and the 80 National Toxicology Program (Nicholson 1986; IARC 1977; Collegium Ramazzini 81 2010). Later, many countries worldwide banned or restricted the use of asbestos 82 containing materials (ACMs). In the countries where asbestos minerals are banned, 83 ACMs have been progressively removed from the environment to minimize exposure of 84 the population (Gualtieri 2012). Despite the huge efforts to entirely remove asbestos from 85 the living environment, some issues are still matter of concern. One of these regards the 86 correct evaluation of the health hazard associated with abandoned asbestos mines 87 (especially dumps and tailings) and natural occurring asbestos (NOA). Mining of 88 asbestos and asbestos associated minerals (e.g., iron oxides) generated vast amounts of 89 residue material, chemically not very different from the original rock (Meyer 1980). An 90 important difference is the fineness of the residue material composing the dumps, making 91 it more prone to weathering or erosion by wind, with subsequent release of fibers in air or 92 in the percolating surface hydrological system. With this premise, Viti et al. (2011) 4 93 suggested that the correct evaluation of the hazard associated with serpentinite outcrops 94 (and asbestos containing mine tailings) would require a careful geo-statistical and geo- 95 mechanical investigation of the fracturing/vein system, followed by careful qualitative 96 and quantitative determinations. Unfortunately, the accomplishment of accurate and 97 precise quantitative figures of the actual asbestos minerals content is made difficult by 98 two major factors: (1) asbestos bearing serpentinite textures typically consist of fine-to- 99 ultrafine intergrowths of fibrous and non-fibrous minerals, often difficult to identify by 100 conventional methods, such as X-ray diffraction or microanalytical approaches. To this 101 aim, DTA seems to be an effective and promising tool of analysis although only a case 102 study has been reported so far (Viti et al. 2011) and further experimental evidence is 103 needed; (2) asbestos and asbestos containing mine dumps and tailings invariably contain 104 high concentrations of asbestos minerals (generally higher than 1wt%). In countries like 105 Italy, regulated experimental techniques for massive materials (X-Ray Powder 106 Diffraction - XRPD, Fourier Transform Infra-red spectroscopy - FTIR, Scanning Electron 107 Microscopy - SEM, and Phase Contrast Optical Microscopy - PCOM) are applied to 108 determine whether asbestos concentration is higher than 0.1 wt% (Italian D.Lgs 109 10/03/2010 nr. 205 All. D). On the same line, Airborne Toxic Control Measure (ATCM) 110 restricted in the USA the use of serpentine and ultramafic rock aggregates for surface 111 applications to materials containing less than 0.25 wt% asbestos determined according to 112 the Californian Air Resources Board method (CARB method 435, 1991). This scenario 113 reveals that accuracy of these quantitative methods have not been tested for highly 114 contaminated massive materials. 115 This work was prompted by the actual need to map the concentration of asbestos 5 116 minerals in abandoned asbestos or asbestos containing open mines with dumps and 117 tailings possibly containing very high concentrations of asbestos fibers (well above 1 118 wt% ). Because the costly reclamation of these sites usually conflicts with the tight 119 budgets of the regional/national funds allocated to such expense items, a step by step long 120 term plan must be proposed with priority given to the reclamation of the areas with the 121 highest asbestos concentration. Therefore, the knowledge of the spatial distribution of the 122 asbestos concentration in such sites is relevant from an economic standpoint as it may 123 permit to prioritize the most hazardous areas within